1. Field of the Invention
The present invention relates to a vertical-type filling and packaging machine for filling a tubular film of synthetic resin with a liquid, semi-liquid, or paste-like filling material and heat-sealing the filled tubular film to thereby form a sacked or flexible packaged product.
2. Description of the Related Art
One conventional vertical-type filling and packaging machine for filling a tubular film of synthetic resin with a liquid, semi,liquid, or paste-like filling material and heat-sealing the filled tubular film to thereby form a sacked or flexible packaged product is shown in FIGS. 1 and 2 of the accompanying drawings. FIG. 1 is a schematic side elevation of the vertical-type filling and packaging machine, and FIG. 2 is a front elevation of the vertical-type filling and packaging machine shown in FIG. 1.
As shown in FIGS. 1 and 2, the vertical-type filling and packaging machine has a charging nozzle 1101 vertically disposed in a charging pipe 1102 for charging a filling material A into a flexible package or sack. The charging pipe 1102 is surrounded by an annular sack forming guide 1103 for forming a sheet film 1120' into a tubular film 1120. The tubular film 1120 which is formed by the sack forming guide 1103 is sealed to join its longitudinal mating edges by a vertical sealer 1104 positioned beneath the sack forming guide 1103.
Below the charging pipe 1102, there are disposed a pair of film feed rollers 1106 in the form of disk-shaped rollers for clamping and feeding the tubular film 1120 downwardly. A pair of squeezing rollers 1107 in the form of cylindrical rollers are disposed below the film feed rollers 1106. The squeezing rollers 1107 are rotatable in synchronism with the film feed rollers 1106 for clamping the tubular film 1120 to divide the charged filling material A into vertically spaced masses in the tubular film 1120. The squeezing rollers 1107 are horizontally movable toward and away from each other perpendicularly to the vertical direction in which the tubular film 1120 is fed downwardly.
A heat sealing device 1108 for horizontally heat-sealing the tubular film 1120 is located downwardly of the squeezing rollers 1107. The heat sealing device 1108 has a pair of horizontally spaced heater bars 1108a each housing a heater (not shown). The heater bars 1108a are horizontally movable toward and away from each other perpendicularly to the vertical direction in which the tubular film 1120 is fed. When the heater bars 1108a that have been moved toward each other are pressed against the tubular film 1120 and heated, the tubular film 1120 is heat-sealed thereby.
A cutting device 1109 is disposed underneath the heat-sealing device 1108 for cooling and cutting off a heat-sealed portion of the tubular film 1120. As shown in FIG. 3 of the accompanying drawings, the cutting device 1109 comprises a pair of blocks 1110a, 1110b disposed in horizontally confronting relationship to each other and movable toward and away from each other in the horizontal directions indicated by the arrows B perpendicularly to the vertical direction in which the tubular film 1120 is fed. The blocks 1110a, 1110b have respective recesses 1115 defined in confronting surfaces thereof in horizontal alignment with each other. One of the blocks 1110a has a coolant passage 1116 defined therein for passing a coolant therethrough to cool the block 1110a. The recess 1115 in the block 1110a houses therein a cutting blade 1111 that is normally retracted in the recess 1115, but can be moved into and out of the recess 115 in the horizontal directions indicated by the arrows B.
A spreader guide 1105 composed of a pair of downwardly spreading pins is mounted on the lower end of the charging pipe 1102.
The tubular film 1120 which is continuously shaped from the sheet film 1120' by the sack forming guide 1103 and the vertical sealer 1104 is fed downwardly by the film feed rollers 1106 rotated by a motor (not shown). At this time, the tubular film 1120 is kept open by the spreader guide 1105. The filling material A is charged into the tubular film 1120 when the film feed rollers 1106 are stopped, and the squeezing rollers 1107, the heat sealing device 1108, and the cutting device 1109 are opened, i.e., spaced from the tubular film 1120. After the filling material A has been charged into the tubular film 1120, the squeezing rollers 1107 are moved into a pressing relationship to the tubular film 1120, thereby diving the charged filling material A into two vertically spaced masses in the tubular film 1120. Thereafter, the squeezing rollers 1107 are rotated in the directions indicated by the arrows in synchronism with the film feed rollers 1106. The tubular film 1120 is now fed downwardly, with an unfilled region 1120a formed in the tubular film 1120 by the squeezing rollers 1107.
When the tubular film 1120 is delivered to the position shown in FIGS. 1 and 2, the squeezing rollers 1107 are deactivated, and the heat sealing device 1108 is closed, i.e., displaced into contact with the unfilled region 1120a of the tubular film 1120. Then, the heat sealing device 1108 is energized to press and heat-seal the unfilled region 1120a. After the unfilled region 1120a has been heat-sealed, the tubular film 1120 is fed downwardly again. When the heat-sealed portion of the tubular film 1120 is positioned in the cutting device 1109, the cutting device 1109 is closed, i.e., displaced into contact with the heat-sealed portion of the tubular film 1120. The cutting device 1109 is pressed against the heat-sealed portion to hold and cool the heat-sealed portion. Then, the cutting blade 1111 is moved out of the recess 1115 in the block 1110a, thereby cutting off the heat-sealed portion of the tubular film 1120.
Another conventional vertical-type filling and packaging machine has a sealing mechanism in which a cutting device similar to the cutting device 1109 is incorporated in a heat sealing device similar to the heat sealing device 1108.
However, the conventional vertical-type filling and packaging machine suffer from the following drawbacks:
(1) After the unfilled region of the tubular film has been heat-sealed and until it is held and pressed by the cutting device, the heat-sealed portion is subject to the weight of the filling material beneath the heat-sealed portion. Since the heat-sealed portion is not completely cooled after the unfilled region of the tubular film has been heat-sealed until it is held and pressed by the cutting device, the heat-sealed portion will be unduly stretched unless the film is of high mechanical strength. Therefore, when a tubular film is to be filled with a heavy material, the tubular film should not be a single-layer film or a thin multilayer film, but should be a laminated film which, as shown in FIG. 4 of the accompanying drawings, comprises an easily heat-fusible film 1126 as of polyethylene for achieving a desired seal strength and a not easily heat-fusible film 1125 as of nylon for achieving a desired mechanical strength, the not easily heat-fusible film 1125 being applied to an outer surface of the easily heat-fusible film 1126.
(2) The easily heat-fusible film and the not easily heat-fusible film are heat-fusible at different temperatures due to different manufacturing processes and conditions. After being heat-sealed, the easily heat-fusible film and the not easily heat-fusible film tend to peel away from each other. Therefore, there are certain limitations as to the selection of film materials and laminating conditions.
(3) Inasmuch as the heat-sealed portion is cut after it is fed to the cutting device, it may be cut at a displaced position owing to a variation in the distance by which the tubular film is fed when moving the heat-sealed portion from the heat sealing device to the cutting device. In view of the range of such displaced positions where the heat-sealed portion may be cut, it is necessary to produce a heat-sealed portion having a large width or vertical extent. However, an increase in the width of the heat-sealed portion results in an increased consumption of the tubular film, which in turn increases the cost of sacked products. In the other conventional vertical-type filling and packaging machine in which the cutting device is incorporated in the heat sealing device, the heat-sealed portion is cut at a desired position because the tubular film is heat-sealed and cut at the same position. However, since a region of the tubular film where the cutting blade passes is not pressed and heat-sealed, the heat-sealed portion is required to have a width increased by an amount corresponding to the region which is not pressed to maintain a desired heat seal strength.
(4) Each of the confronting surfaces of the respective heater bars has an array of horizontal ridges for preventing the heat-sealed film layers from peeling away from each other before the heat-sealed portion reaches the cutting device. When the heat sealing device is pressed against the tubular film, the horizontal ridges bite into the tubular film, causing the film layers to mesh with each other, thereby keeping the heat-sealed film layers bonded to each other while they are being solidified. As shown in FIG. 5 of the accompanying drawings, however, separate or non-bonded regions 1121a are created between bonded regions 1121b of the film layers. Since any filling material which is left in the non-bonded regions 1121a tends to foam with the heat of the heater bars, the film layers in the bonded regions 1121b may peel away from each other. Furthermore, if the tubular film is cut at any one of the non-bonded regions 1121a, the filling material which is left in the cut-off non-bonded region 1121a will be exposed, and will leak and rot, giving off an undesirable odor which is detrimental to the value of the sacked products.
(5) Inasmuch as the horizontal ridges of the heater bars are positioned so as to mesh with each other when the heat sealing device is pressed against the tubular film, the tubular film is liable to be severed by the edges of intermeshing horizontal ridges. When such a film severance occurs, the filling and packaging machine is often caused to shut off for a prolonged period of time.